using HTTPHandler cause Django server side shows http 400 and Invalid HTTP_HOST header message

[iMath]

> Are you sure you posted the code you are actually using? Because the 
> error message suggests a difference.
> 
I am sure !

As I have tested: If I pass the IP address of my web server to the host parameter of HTTPHandler, the server side would show http 400 and Invalid HTTP_HOST header message  , while if I pass the domain name instead, then the view function works as expected . 
 
would it be a bug within HTTPHandler?